这次的例子是使用会话给上一个例子添加登陆功能
1、页面逻辑
- 首先是登陆页面，这里需要输入账号和密码，输入正确后将进入商品列表页面，输入错误将会提示账号或者密码错误
- 其次是商品列表和购物车页面，添加了注销的链接
2、JSP
- 登陆页面的JSP，,loginFailed若为true表示用户已经尝试登陆且登陆出错，若为false表示用户还没用尝试登陆
<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>login application</title> </head> <body> <h2>Login</h2> You must log in to access the customer support site.<br /><br /> <% if(((Boolean)request.getAttribute("loginFailed"))) { %> <b>The username or password you entered are not correct. Please try again.</b><br /><br /> <% } %> <form method="POST" action="<c:url value="/login" />"> Username<br /> <input type="text" name="username" /><br /><br /> Password<br /> <input type="password" name="password" /><br /><br /> <input type="submit" value="Log In" /> </form> </body> </html>
- 然后就是把这行代码加到商品列表和购物车页面
<a href="<c:url value="/login?logout=false" />">Logout</a>
3、代码逻辑
- 先是简单的建立账号密码数据库
private static final Map<String, String> userDatabase = new Hashtable<>(); static { userDatabase.put("user1","password1"); userDatabase.put("user2","password2"); userDatabase.put("user3","password3"); userDatabase.put("user4","password4"); }
- 然后是doGet方法的逻辑，注销的链接是直接重定向到登陆页面的，所以登陆页面先是判断是否需要清空Session，然后通过username检测是否已经登陆过了，然后就是将loginFailed设为false并将请求转发给login.jsp
@Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); if(request.getParameter("logout") != null) { request.getSession().invalidate(); response.sendRedirect("login"); return; }else if(session.getAttribute("username" )!= null) { response.sendRedirect("shop"); return; } request.setAttribute("loginFailed",false); request.getRequestDispatcher("/WEB-INF/jsp/view/login.jsp") .forward(request, response); }
- doPost将在用户点击提交时被调用，同样首先通过username检测是否已经登陆过，如果没有登陆过将检查账号密码是否有问题，没有问题重定向到商品列表页面，如果有问题的话将会把loginFailed设为true并将请求转发给login.jsp
@Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpSession session = request.getSession(); if(session.getAttribute("username" )!= null) { response.sendRedirect("shop"); return; } String username = request.getParameter("username"); String password = request.getParameter("password"); if(username == null || password == null || !LoginServlet.userDatabase.containsKey(username)|| !password.equals(LoginServlet.userDatabase.get(username))){ request.setAttribute("loginFailed",true); request.getRequestDispatcher("/WEB-INF/jsp/view/login.jsp") .forward(request,response); } else { session.setAttribute("username", username); request.changeSessionId(); response.sendRedirect("shop"); } }